TFRC promotes ferroptosis to suppress breast cancer bone metastasis via the activation of HIF-1 pathway.

BACKGROUND: Breast cancer with bone metastasis remains a significant clinical challenge. Ferroptosis, an iron-dependent cell death process, may influence metastasis. However, the role of key regulators like transferrin receptor (TFRC) is unclear. METHODS: Transcriptome sequencing identified ferroptosis-related differentially expressed genes (DEGs) in tibial tumors from a breast cancer mouse model with bone metastasis versus breast cancer cells. Hub genes were identified via protein-protein interaction network analysis. The function of TFRC was validated in vitro (MCF-7 and MDA-MB-231) through gain/loss-of-function studies combined with ferroptosis modulators (Erastin, Ferrostatin-1) and in a BALB/c nude mouse intratibial model. Cell apoptosis, proliferation, invasion, and migration were evaluated by flow cytometry, cell-counting kit-8, Transwell, and wound healing assays, respectively. Ferroptosis markers and epithelial-mesenchymal transition-related proteins were assessed. The involvement of the hypoxia-inducible factor-1 (HIF-1) pathway was investigated using the HIF-1α inhibitor PX-478. RESULTS: Bioinformatics identified 22 ferroptosis-related DEGs, with TFRC among the top 10 hub genes significantly downregulated in bone metastasis, a finding corroborated in human clinical specimens. Overexpressing TFRC in vivo suppressed tumor growth, upregulated E-cadherin, downregulated N-cadherin, and promoted ferroptosis. In vitro, TFRC overexpression consistently inhibited malignant phenotypes and induced ferroptosis in both cell lines, effects reversible by ferroptosis inhibition. Conversely, ferroptosis activation upregulated TFRC expression, and TFRC knockdown attenuated cellular sensitivity to ferroptosis inducers, indicating a reciprocal regulatory relationship. Mechanistically, HIF-1 pathway was identified as the downstream pathway of TFRC, and TFRC overexpression upregulated HIF-1α. PX-478 attenuated TFRC-mediated ferroptosis induction and suppression of malignancy. CONCLUSION: TFRC inhibits bone metastasis in breast cancer by promoting ferroptosis via HIF-1α activation, highlighting its potential as a therapeutic target.